JP2001303185A - High tensile strength cold rolled steel sheet excellent in ductility and strain age hardening characteristic and method for producing high tensile strength cold rolled steel sheet - Google Patents

High tensile strength cold rolled steel sheet excellent in ductility and strain age hardening characteristic and method for producing high tensile strength cold rolled steel sheet

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Publication number
JP2001303185A
JP2001303185A JP2000127705A JP2000127705A JP2001303185A JP 2001303185 A JP2001303185 A JP 2001303185A JP 2000127705 A JP2000127705 A JP 2000127705A JP 2000127705 A JP2000127705 A JP 2000127705A JP 2001303185 A JP2001303185 A JP 2001303185A
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JP
Japan
Prior art keywords
steel sheet
rolled steel
ductility
tensile strength
strain
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
JP2000127705A
Other languages
Japanese (ja)
Other versions
JP4524850B2 (en
Inventor
Takashi Sakata
坂田　　敬
Akio Tosaka
章男 登坂
Osamu Furukimi
古君　　修
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
JFE Steel Corp
Original Assignee
Kawasaki Steel Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to JP2000127705A priority Critical patent/JP4524850B2/en
Application filed by Kawasaki Steel Corp filed Critical Kawasaki Steel Corp
Priority to CA2377701A priority patent/CA2377701C/en
Priority to KR1020017016595A priority patent/KR100592211B1/en
Priority to TW090103284A priority patent/TWI238855B/en
Priority to US10/009,957 priority patent/US6692584B2/en
Priority to EP01904407A priority patent/EP1207213B1/en
Priority to CNB018017673A priority patent/CN1147610C/en
Priority to DE60110346T priority patent/DE60110346T2/en
Priority to PCT/JP2001/001006 priority patent/WO2001083839A1/en
Publication of JP2001303185A publication Critical patent/JP2001303185A/en
Application granted granted Critical
Publication of JP4524850B2 publication Critical patent/JP4524850B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0273—Final recrystallisation annealing
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold rolling

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Sheet Steel (AREA)

Abstract

PROBLEM TO BE SOLVED: To produce a high tensile strength cold rolled steel sheet excellent in ductility and strain age hardening characteristics and further excellent in impact resistance and to provide its producing method. SOLUTION: A thin cold rolled steel sheet having a composition containing 0.05 to 0.30% C, 0.4 to 2.0% Si, 0.7 to 3.0% Mn, <=0.08% P, <=0.02% Al and 0.0050 to 0.0250% N and an N/Al ratio satisfying >=0.3 is heated at (Ac1 transformation point) to (Ac3 transformation point + 50 deg.C), is then cooled at least in the range of 600 to 500 deg.C at a cooling rate of 5 to 150 deg.C/s and is held in the temperature range of 350 to 500 deg.C. In this way, the steel sheet is provided with excellent ductility and strain age hardening characteristics attaining ΔTs of >=50 MPa, and its impact resistance is improved.

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【０００１】[0001]

【発明の属する技術分野】本発明は、主として自動車車
体用として好適な高加工性高張力冷延鋼板に係り、とく
に引張強さ（ＴＳ）440MPa以上で、延性および歪時効硬
化特性に優れた高張力冷延鋼板、およびその製造方法に
関する。本発明の高張力冷延鋼板は、軽度の曲げ加工や
ロールフォーミングによりパイプに成形されるような比
較的軽加工に供されるものから比較的厳しい絞り成形に
供されるものまで、広範囲の用途に適するものである。
なお、本発明における鋼板とは、鋼板、鋼帯を含むもの
とする。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-workability, high-tensile cold-rolled steel sheet suitable mainly for use in an automobile body, and more particularly to a high-strength steel sheet having a tensile strength (TS) of 440 MPa or more and excellent ductility and strain age hardening characteristics. The present invention relates to a cold-rolled tension steel sheet and a method for producing the same. The high-tensile cold-rolled steel sheet of the present invention can be used in a wide range of applications, from those subjected to relatively light working such as forming into pipes by light bending and roll forming to those subjected to relatively severe drawing. It is suitable for.
In addition, the steel sheet in the present invention includes a steel sheet and a steel strip.

【０００２】また、本発明において、「歪時効硬化特性
に優れた」とは、引張歪５％の予変形後、170 ℃の温度
に20min 保持する条件で時効処理したとき、この時効処
理前後の変形応力増加量（ＢＨ量と記す；ＢＨ量＝時効
処理後の降伏応力−時効処理前の予変形応力）が40MPa
以上であり、かつ歪時効処理（前記予変形＋前記時効処
理）前後の引張強さ増加量（ΔＴＳと記す；ΔＴＳ＝時
効処理後の引張強さ−予変形前の引張強さ）が50MPa 以
上であることを意味する。In the present invention, "excellent in strain aging hardening characteristics" means that after pre-deformation with a tensile strain of 5%, aging treatment is performed at a temperature of 170 ° C. for 20 minutes before and after the aging treatment. Deformation stress increase (BH amount; BH amount = yield stress after aging treatment-pre-deformation stress before aging treatment) is 40 MPa
And the increase in tensile strength before and after the strain aging treatment (pre-deformation + aging treatment) (noted as ΔTS; ΔTS = tensile strength after aging treatment-tensile strength before pre-deformation) is 50 MPa or more. Means that

【０００３】[0003]

【従来の技術】昨今の地球環境問題からの排出ガス規制
に関連し、自動車における車体重量の軽減は極めて重要
な課題となっている。自動車の車体重量軽減のために
は、多量に使用されている鋼板の強度を増加させ、すな
わち高張力鋼板を適用して、使用する鋼板の薄肉化を図
るのが有効である。2. Description of the Related Art Reduction of vehicle body weight in automobiles has become an extremely important issue in connection with recent emission regulations due to global environmental problems. In order to reduce the body weight of an automobile, it is effective to increase the strength of a steel plate used in large quantities, that is, to apply a high-tensile steel plate to reduce the thickness of the steel plate used.

【０００４】しかし、薄肉の高張力鋼板を使用した自動
車部品でも、その役割に応じて課されるパフォーマンス
が必要十分に発揮されねばならない。かかるパフォーマ
ンスとしては、例えば曲げ、ねじり変形に対する静的強
度、耐疲労性、耐衝撃特性などがある。したがって、自
動車部品に適用される高張力鋼板は、成形加工後にかか
る特性にも優れることが必要となる。[0004] However, even in the case of automobile parts using thin high-strength steel sheets, the performance imposed in accordance with their roles must be sufficiently exhibited. Such performance includes, for example, static strength against bending and torsion deformation, fatigue resistance, impact resistance, and the like. Therefore, a high-strength steel sheet applied to an automobile part needs to have excellent properties after forming.

【０００５】また、自動車部品を製造する過程において
は、鋼板に対してプレス成形が行われるが、鋼板の強度
が高すぎるとプレス成形した場合には、 形状凍結性が劣化する、 延性が劣化するため成形時に割れやネッキングなどの
不具合を生ずる、 耐デント性（局部的な圧縮荷重負荷により生ずる凹み
に対する耐性）が劣化する、といった問題が生じ、自動
車車体への高張力鋼板の適用拡大を阻んでいた。[0005] In the process of manufacturing automobile parts, press forming is performed on a steel sheet. If the strength of the steel sheet is too high, press-forming deteriorates the shape freezing property and the ductility. As a result, problems such as cracking and necking occur during molding, and dent resistance (resistance to dents caused by local compressive load) deteriorates, which hinders the application of high-tensile steel sheets to automobile bodies. Was.

【０００６】これを打開するための手法として、例えば
外板パネル用の冷延鋼板では、極低炭素鋼を素材とし、
最終的に固溶状態で残存するＣ量を適正範囲に制御した
鋼板が知られている。この種の鋼板は、プレス成形時に
は軟質に保たれ、形状凍結性、延性を確保し、プレス成
形後に行われる、170 ℃×20min 程度の塗装焼付工程で
起こる歪時効硬化現象を利用した降伏応力の上昇を得
て、耐デント性を確保しようとするものである。この種
鋼板では、プレス成形時にはＣが鋼中に固溶して軟質で
あり、一方、プレス成形後には、塗装焼付工程で、プレ
ス成形時に導入された転位に固溶Ｃが固着して、降伏応
力が上昇する。[0006] As a method for overcoming this, for example, in the case of cold-rolled steel sheets for outer panel, ultra-low carbon steel is used as a material.
There is known a steel sheet in which the amount of C finally remaining in a solid solution state is controlled to an appropriate range. This type of steel sheet is kept soft during press forming, secures shape freezing and ductility, and has a yield stress that utilizes the strain aging hardening phenomenon that occurs in the paint baking process at 170 ° C × 20 min after press forming. The aim is to secure the dent resistance by obtaining a rise. In this type of steel sheet, during press forming, C forms a solid solution in the steel and is soft. On the other hand, after press forming, in the coating baking process, solid solution C adheres to dislocations introduced during press forming, yielding Stress increases.

【０００７】しかし、この種鋼板では、表面欠陥となる
ストレーッチャーストレインの発生を防止する観点か
ら、歪時効硬化による降伏応力上昇量は低く抑えられて
いる。このため、実際に部品の軽量化に寄与するところ
は小さいことになる。すなわち、部品の軽量化には、単
に歪時効により降伏応力のみ上昇するのではなく、さら
に変形が進んだときの強度特性の上昇が必要である。言
い換えれば、歪時効後の引張強さの上昇が望まれてい
る。However, in this type of steel sheet, the yield stress increase due to strain age hardening is suppressed low from the viewpoint of preventing the occurrence of a strainer strain that becomes a surface defect. For this reason, the portion that actually contributes to the weight reduction of components is small. That is, in order to reduce the weight of a component, it is necessary to increase not only the yield stress due to strain aging but also the strength characteristics when the deformation is further advanced. In other words, an increase in tensile strength after strain aging is desired.

【０００８】一方、外観があまり問題にならない用途に
対しては、固溶Ｎを用いて焼付硬化量をさらに増加させ
た鋼板や、組織をフェライトとマルテンサイトからなる
複合組織とすることで焼付硬化性をより一層向上させた
鋼板が提案されている。例えば、特開昭60-52528号公報
には、Ｃ：0.02〜0.15％、Mn：0.8 〜3.5 ％、Ｐ：0.02
〜0.15％、Al：0.10％以下、Ｎ：0.005 〜0.025 ％を含
む鋼を550 ℃以下の温度で巻き取る熱間圧延と、冷延後
の焼鈍を制御冷却熱処理とする延性およびスポット溶接
性がともに良好な高強度薄鋼板の製造方法が開示されて
いる。特開昭60-52528号公報に記載された技術で製造さ
れた鋼板は、フェライトとマルテンサイトを主体とする
低温変態生成物相からなる混合組織を有し延性に優れる
とともに、積極的に添加されたＮによる塗装焼付けの際
の歪時効を利用して、高強度を得ようとするものであ
る。On the other hand, for applications in which the appearance does not matter so much, baking hardening is performed by using a steel sheet in which the amount of bake hardening is further increased by using solid solution N, or by forming a composite structure of ferrite and martensite. A steel sheet with further improved properties has been proposed. For example, JP-A-60-52528 discloses that C: 0.02 to 0.15%, Mn: 0.8 to 3.5%, P: 0.02%.
Up to 0.15%, Al: 0.10%, N: 0.005 to 0.025%, hot rolling at a temperature of 550 ° C or less, and ductility and spot weldability, where annealing after cold rolling is controlled cooling heat treatment. A method for producing a high-strength thin steel sheet that is good in both cases is disclosed. The steel sheet manufactured by the technique described in JP-A-60-52528 has a mixed structure composed of a low-temperature transformation product phase mainly composed of ferrite and martensite, has excellent ductility, and is actively added. The purpose of the present invention is to obtain high strength by utilizing strain aging at the time of paint baking with N.

【０００９】しかしながら、特開昭60-52528号公報に記
載された技術では、歪時効硬化による降伏応力ＹＳの増
加量は大きいが引張強さＴＳの増加量が少なく、また、
降伏応力ＹＳの増加量も大きくばらつくなど機械的性質
の変動も大きいため、現状で要望されている自動車部品
の軽量化に寄与できるほどの鋼板の薄肉化が期待できな
い。However, according to the technique described in Japanese Patent Application Laid-Open No. 60-52528, the increase in the yield stress YS due to strain age hardening is large, but the increase in the tensile strength TS is small.
Since there is a large variation in mechanical properties such as a large increase in the yield stress YS and a large variation, it is not possible to expect a steel sheet to be thin enough to contribute to a reduction in the weight of automobile parts currently demanded.

【００１０】また、組織を、フェライト、ベイナイトと
残留オーステナイトからなる複合組織として、延性を顕
著に向上させた、いわゆる変態誘起塑性型鋼板（ＴＲＩ
Ｐ鋼）が提案されている。例えば、特開昭61-217529 号
公報には、Ｃ：0.12〜0.70％、Si：0.4 〜1.8 ％、Mn：
0.2 〜2.5 ％、Al：0.01〜0.07％、Ｎ：0.02％以下を含
み、残部Feおよび不可避的不純物からなる鋼板に連続焼
鈍の条件を制御した焼鈍を施すことを特徴とする延性に
優れた高強度鋼板の製造方法が提案されている。しかし
ながら、特開昭61-217529 号公報に記載された技術で製
造された鋼板は、ＮをAlによりAlNとして析出させるこ
とで延性の向上を図っており、Ｃ、Ｎ等の侵入型元素が
ほとんど存在しないため、プレス成形後の塗装焼付処理
によって、強度の増加がほとんど期待できない。そのた
め、完成部品の強度が著しく低く、耐衝撃性が強く要求
される用途への適用ができないという問題が残されてい
た。また、特開昭61−217529号公報に記載された技術で
製造された鋼板は、同一強度で比較するとSi、Mn等の含
有量が高くなり、塗装性、溶接性に難点がある。A so-called transformation induced plasticity steel sheet (TRI) having a remarkably improved ductility as a composite structure comprising ferrite, bainite and retained austenite.
P steel) has been proposed. For example, JP-A-61-217529 discloses that C: 0.12 to 0.70%, Si: 0.4 to 1.8%, Mn:
A steel sheet containing 0.2 to 2.5%, Al: 0.01 to 0.07%, and N: 0.02% or less, characterized by subjecting a steel sheet consisting of the balance of Fe and unavoidable impurities to annealing under controlled continuous annealing conditions, characterized by excellent ductility. A method for producing a high strength steel sheet has been proposed. However, steel sheets manufactured by the technology described in Japanese Patent Application Laid-Open No. 61-217529 aim at improving ductility by precipitating N as AlN with Al, and almost no interstitial elements such as C and N are present. Since it does not exist, almost no increase in strength can be expected by the coating baking treatment after press molding. Therefore, there remains a problem that the strength of the finished part is extremely low, and it cannot be applied to applications that require strong impact resistance. Further, a steel sheet manufactured by the technique described in JP-A-61-217529 has a high content of Si, Mn, etc. when compared at the same strength, and has drawbacks in paintability and weldability.

【００１１】また、乗員の安全性向上の観点から、プレ
ス成形時には軟質で加工性に優れ、加工後に塗装焼付処
理等の熱処理により降伏応力の増加に加えて、引張強さ
もともに高強度となり、部品強度を高くできる、加工性
と耐衝撃特性がともに改善された鋼板が要望されてい
る。このような要望に対し、例えば、特開平10-310824
号公報、特開平10-310847号公報には、Ｃ：0.01〜0.08
％、Si：0.005 〜1.0 ％、Mn：0.01〜3.0 ％、Al：0.00
1 〜0.1 ％、Ｎ：0.0002〜0.01％を含み、さらにＷ、C
r、Moの１種または２種以上を合計量が0.05〜3.0 ％含
有し、組織がフェライトあるいはフェライトを主体とす
る成形後強度上昇熱処理性能を有する合金化溶融亜鉛め
っき鋼板およびその製造方法が開示されている。ここで
いう、成形後強度上昇熱処理性能とは、２％以上の歪が
加わる成形加工後、200 〜450 ℃で加熱する熱処理を施
して、熱処理前の引張強さに比べ、熱処理後の引張強さ
が増加する性能をいう。しかしながら、特開平10-31082
4 号公報、特開平10-310847 号公報に記載された技術で
製造された鋼板では、塗装焼付処理を従来（170 ℃）よ
り高い200 〜450 ℃という温度で行う必要があり、部品
製造の生産性が低下し経済的に不利となるという問題が
あった。[0011] From the viewpoint of improving the safety of the occupant, it is soft and excellent in workability at the time of press forming, and in addition to an increase in yield stress and a high tensile strength due to heat treatment such as paint baking after working, the components have high tensile strength. There is a demand for a steel sheet that can increase the strength and has improved workability and impact resistance. In response to such a request, for example, Japanese Patent Laid-Open No. 10-310824
JP-A-10-310847, C: 0.01 to 0.08
%, Si: 0.005 to 1.0%, Mn: 0.01 to 3.0%, Al: 0.00
1-0.1%, N: 0.0002-0.01%, W, C
Disclosed is an alloyed hot-dip galvanized steel sheet containing one or more kinds of r and Mo in a total amount of 0.05 to 3.0% and having a heat treatment performance of increasing strength after forming, mainly composed of ferrite or ferrite, and a method for producing the same. Have been. As used herein, the post-molding strength increase heat treatment performance refers to the tensile strength after heat treatment, which is performed after heat treatment at 200 to 450 ° C. Is the performance that increases. However, JP 10-31082
No. 4 and Japanese Patent Application Laid-Open No. 10-310847, the steel plate manufactured by the technique described above requires a paint baking treatment at a temperature of 200 to 450 ° C., which is higher than the conventional (170 ° C.). There is a problem that performance is reduced and it is disadvantageous economically.

【００１２】さらに、上記した従来の鋼板では、単純な
引張試験による塗装焼付処理後の強度評価では優れてい
るものの、実プレス条件にしたがって、塑性変形させた
ときの強度に大きなばらつきが存在し、信頼性が要求さ
れる部品に適用するには必ずしも十分とはいえなかった
のである。Further, the above-mentioned conventional steel sheet is excellent in the strength evaluation after the paint baking treatment by a simple tensile test, but has a large variation in the strength when plastically deformed according to the actual pressing conditions. It was not always enough to be applied to parts that required reliability.

【００１３】[0013]

【発明が解決しようとする課題】本発明は、上記した従
来技術の限界を打破し、高い延性と、自動車部品に成形
したのちに自動車部品として十分な強度が得られ自動車
車体の軽量化に充分に寄与できる、歪時効硬化特性に優
れ、さらに耐衝撃特性に優れた高張力冷延鋼板およびこ
れら鋼板を工業的に安価に、かつ安定して製造できる製
造方法を提供することを目的とする。本発明における歪
時効硬化特性は、引張歪５％の予変形後、170 ℃の温度
に20min 保持する時効条件で、ＢＨ量が40MPa 以上、Δ
ＴＳが50MPa 以上を目標とする。DISCLOSURE OF THE INVENTION The present invention overcomes the limitations of the prior art described above, and provides high ductility and sufficient strength as an automobile part after being formed into an automobile part. It is an object of the present invention to provide a high-tensile cold-rolled steel sheet having excellent strain aging hardening characteristics and excellent impact resistance, and a method for industrially inexpensively and stably manufacturing these steel sheets. The strain aging hardening characteristics in the present invention are as follows. Under aging conditions of preserving a tensile strain of 5% and maintaining the temperature at 170 ° C. for 20 minutes, a BH amount of 40 MPa or more, Δ
The target of TS is 50MPa or more.

【００１４】[0014]

【課題を解決するための手段】本発明者らは、上記課題
を達成するために、組成および製造条件を種々変化して
鋼板を製造し、多くの材質評価実験を行った。その結
果、高加工性が要求される分野では従来あまり積極的に
利用されることがなかったＮを強化元素として利用し、
他の合金元素を低減し、さらに加えて、この強化元素
（Ｎ）の作用により発現する大きな歪時効硬化現象を有
利に活用することにより、プレス成形性の向上と、プレ
ス成形後の高強度化とを容易に両立させることができる
ことを知見した。Means for Solving the Problems In order to achieve the above object, the present inventors manufactured steel sheets with various compositions and manufacturing conditions, and conducted many material evaluation experiments. As a result, in fields where high workability is required, N, which has not been actively used in the past, is used as a strengthening element,
By reducing other alloying elements, and in addition, by taking advantage of the large strain age hardening phenomenon developed by the action of the strengthening element (N), improvement of press formability and enhancement of strength after press forming Have been found to be easily compatible.

【００１５】またさらに、本発明者らは、加熱冷却条件
を含め、冷延板の焼鈍条件を調整することにより、組織
をフェライト、ベイナイトと残留オーステナイトとから
なる複合組織とすることができ、延性が顕著に向上して
プレス成形性が向上するとともに、固溶Ｎ量を適正値に
調整することができ、Ｎによる大きな歪時効硬化現象を
有利に活用するができ、自動車部品の耐衝撃特性を顕著
に向上できることを知見した。Further, the present inventors can adjust the annealing conditions of the cold-rolled sheet, including the heating and cooling conditions, so that the structure can be a composite structure composed of ferrite, bainite and retained austenite, Notably, the press formability is improved, the amount of dissolved N can be adjusted to an appropriate value, the large strain age hardening phenomenon due to N can be advantageously used, and the impact resistance of automobile parts can be improved. It was found that it could be significantly improved.

【００１６】本発明は、上記した知見に基づいて、さら
に検討を加え完成したものである。すなわち、第１の本
発明は、質量％で、Ｃ：0.05〜0.30％、Si：0.4 〜2.0
％、Mn：0.7 〜3.0 ％、Ｐ：0.08％以下、Al：0.02％以
下、Ｎ：0.0050〜0.0250％を含み、かつＮ／Alが0.3 以
上、固溶状態のＮを0.0010％以上含有し、残部Feおよび
不可避的不純物からなる組成と、体積率で、20〜80％の
フェライト相と、10〜60％のベイナイト相と、3.0 ％以
上の残留オーステナイト相とを含む複合組織を有するこ
とを特徴とする延性およびΔＴＳ：50MPa 以上となる歪
時効硬化特性に優れた高張力冷延鋼板であり、また、第
１の本発明では、前記組成に加えてさらに、質量％で、
次ａ群〜ｃ群 ａ群：Ｂ：0.0003〜0.01％、Cu：0.005 〜1.5 ％、Ni：
0.005 〜1.5 ％、Cr：0.05〜1.0 ％のうちの１種または
２種以上 ｂ群：Ti、Nb、Ｖ、Zrのうちの１種または２種以上を合
計で0.002 〜0.03％ ｃ群：Ca、REM の１種または２種を合計で0.0010〜0.01
0 ％のうちの１群または２群以上を含むことが好まし
い。The present invention has been completed by further study based on the above findings. That is, in the first invention, C: 0.05 to 0.30% and Si: 0.4 to 2.0 in mass%.
%, Mn: 0.7 to 3.0%, P: 0.08% or less, Al: 0.02% or less, N: 0.0050 to 0.0250%, N / Al is 0.3 or more, and N in solid solution is 0.0010% or more, It is characterized by having a composite structure comprising a composition consisting of the balance of Fe and unavoidable impurities, a ferrite phase of 20 to 80% by volume, a bainite phase of 10 to 60%, and a residual austenite phase of 3.0% or more. It is a high-tensile cold-rolled steel sheet excellent in ductility and strain aging hardening property of ΔTS: 50 MPa or more, and in the first present invention, in addition to the above composition, further,
Next groups a to c: a group: B: 0.0003 to 0.01%, Cu: 0.005 to 1.5%, Ni:
0.005 to 1.5%, Cr: one or more of 0.05 to 1.0% b group: one or more of Ti, Nb, V, and Zr 0.002 to 0.03% in total C group: Ca , REM 1 or 2 in total 0.0010-0.01
It is preferable to include one or more of 0%.

【００１７】また、第１の本発明では、前記高張力冷延
鋼板の板厚が3.2 mm以下の薄鋼板であることが好まし
い。また、第２の本発明は、質量％で、Ｃ：0.05〜0.30
％、Si：0.4 〜2.0 ％、Mn：0.7 〜3.0 ％、Ｐ：0.08％
以下、Al：0.02％以下、Ｎ：0.0050〜0.0250％を含み、
かつＮ／Alが0.3 以上を含有する薄冷延鋼板に、加熱温
度を（Ａc1変態点）〜（Ａc3変態点＋50℃）の間の温度
とする焼鈍処理と、ついで該加熱温度から、少なくとも
600 ℃から500 ℃の範囲を５〜 150℃／ｓの冷却速度で
冷却し、350〜500 ℃の温度範囲で30ｓ以上の保持を行
う冷却・保持処理を施すことを特徴とする、延性および
ΔＴＳ：50MPa 以上となる歪時効硬化特性に優れた高張
力冷延鋼板の製造方法である。In the first aspect of the present invention, the high-tensile cold-rolled steel sheet is preferably a thin steel sheet having a thickness of 3.2 mm or less. Further, the second present invention is based on the mass%, C: 0.05 to 0.30.
%, Si: 0.4 to 2.0%, Mn: 0.7 to 3.0%, P: 0.08%
Hereinafter, Al: 0.02% or less, N: 0.0050 to 0.0250%,
And an annealing treatment in which the heating temperature is set to a temperature between (Ac 1 transformation point) to (Ac 3 transformation point + 50 ° C.) on the thin cold-rolled steel sheet containing N / Al of 0.3 or more. at least
The ductility and ΔTS are characterized in that a cooling range of 600 to 500 ° C. is cooled at a cooling rate of 5 to 150 ° C./s, and a cooling / holding process is performed to maintain the temperature range of 350 to 500 ° C. for 30 seconds or more. : A method for producing a high-tensile cold-rolled steel sheet having excellent strain age hardening characteristics of 50 MPa or more.

【００１８】[0018]

【発明の実施の形態】まず、本発明鋼板の組成限定理由
について説明する。なお、質量％は、以下、単に％と記
す。 Ｃ：0.05〜0.25％ Ｃは、鋼板の強度を増加する元素であり、また、オース
テナイト（γ）相に濃化してγ相を安定化する元素であ
り、本発明では、強度と、所望の残留γ量を確保するた
めに0.05％以上の含有を必要とする。一方、0.25％を超
える含有は、溶接性を著しく劣化させる。このため、Ｃ
は0.05〜0.25％の範囲に限定する。なお、極めて高い延
性と溶接性の両立という観点からは、0.07〜0.18％とす
るのが好ましい。First, the reasons for limiting the composition of the steel sheet of the present invention will be described. Hereinafter, the mass% is simply described as%. C: 0.05 to 0.25% C is an element that increases the strength of the steel sheet, and is an element that is concentrated into an austenite (γ) phase to stabilize the γ phase. In order to secure the γ content, the content of 0.05% or more is required. On the other hand, when the content exceeds 0.25%, the weldability is significantly deteriorated. Therefore, C
Is limited to the range of 0.05 to 0.25%. In addition, from the viewpoint of achieving both extremely high ductility and weldability, the content is preferably set to 0.07 to 0.18%.

【００１９】Si：0.4 〜2.0 ％ Siは、鋼の延性を顕著に低下させることなく鋼板を高強
度化させることができる有用な元素であり、さらにはγ
がベイナイトへ変態する際に炭化物の生成を抑制するこ
とにより、未変態γの安定性を増加させる効果を有する
元素である。このような効果は0.4 ％以上の含有で認め
られる。一方、2.0 ％を超える含有は、効果が飽和する
うえ、表面性状、化成処理性などの表面美麗性に悪影響
をあたえる。このため、Siは0.4 〜2.0 ％の範囲に限定
した。なお、好ましくは、0.6 〜1.5 ％である。Si: 0.4 to 2.0% Si is a useful element capable of increasing the strength of a steel sheet without remarkably reducing the ductility of the steel.
Is an element having the effect of increasing the stability of untransformed γ by suppressing the formation of carbides when transformed to bainite. Such an effect is observed at a content of 0.4% or more. On the other hand, a content exceeding 2.0% saturates the effect and adversely affects the surface aesthetics such as surface properties and chemical conversion treatment. For this reason, Si is limited to the range of 0.4 to 2.0%. Preferably, the content is 0.6 to 1.5%.

【００２０】Mn：0.5 〜3.0 ％ Mnは、焼入れ性を向上させる元素であり、鋼板強度の増
加に大きく寄与する。また、MnはＳによる熱間割れを防
止する有効な元素であり、含有するＳ量により添加する
のが好ましい。さらにMnは、γ相に濃化し、焼入れ性を
向上させるうえ、γ相に濃縮し残留γを安定化する効果
を有する。このような効果は0.5 ％以上の含有で認めら
れるが、3.0 ％を超える含有は、上記した効果が飽和す
るうえ、スポット溶接性が顕著に劣化する。このため、
Mnは0.5 〜3.0 ％に限定した。なお、好ましくは0.9 〜
2.0 ％である。Mn: 0.5-3.0% Mn is an element that improves the hardenability and greatly contributes to an increase in the strength of the steel sheet. Further, Mn is an effective element for preventing hot cracking due to S, and is preferably added depending on the amount of S contained. Further, Mn has an effect of concentrating in γ phase to improve hardenability and concentrating in γ phase to stabilize residual γ. Such an effect is recognized at a content of 0.5% or more, but when the content is more than 3.0%, the above-mentioned effects are saturated and the spot weldability is remarkably deteriorated. For this reason,
Mn was limited to 0.5-3.0%. Preferably, 0.9 to
2.0%.

【００２１】Ｐ：0.08％以下 Ｐは、鋼の固溶強化元素として、また延性やｒ値の改善
に有用な元素であるが、過剰に含有すると鋼を脆化さ
せ、さらに鋼板の伸びフランジ加工性を低下させる。ま
た、Ｐは鋼中で偏析する傾向が強いためそれに起因した
溶接部の脆化をもたらす。このため、Ｐは0.08％以下に
限定した。なお、伸びフランジ加工性や溶接部靱性が特
に重要視される場合は0.04％以下とするのが好ましい。
なお、より好ましくは溶接部靱性の観点から0.02％以下
である。P: 0.08% or less P is an element useful as a solid solution strengthening element for steel and is useful for improving ductility and r-value. Reduce the nature. In addition, P has a strong tendency to segregate in steel, which results in embrittlement of the weld. Therefore, P is limited to 0.08% or less. When stretch flangeability and weld toughness are particularly important, the content is preferably 0.04% or less.
The content is more preferably 0.02% or less from the viewpoint of weld toughness.

【００２２】Al：0.02％以下 Alは、溶製時に脱酸剤として作用し鋼の清浄度を向上さ
せるとともに、さらに組織の微細化に有効な元素であ
り、本発明では0.005 ％以上含有するのが望ましい。一
方、過剰なAl含有は、鋼板表面の清浄性を悪化させ、さ
らに固溶状態のＮを減少させ、歪時効硬化現象に寄与す
る固溶Ｎの不足を生じ、本発明の特徴である歪時効硬化
特性を低下させる。このため、本発明では、Alは0.02％
以下と低く限定する。なお、安定して高い歪時効硬化特
性を得るためには、0.015 ％以下である。Al: 0.02% or less Al acts as a deoxidizing agent at the time of smelting to improve the cleanliness of the steel and is an element effective for further refining the structure. In the present invention, Al is contained in an amount of 0.005% or more. Is desirable. On the other hand, an excessive Al content deteriorates the cleanliness of the steel sheet surface, further reduces the N in the solid solution state, causes a shortage of the solid solution N contributing to the strain aging hardening phenomenon, and the strain aging characteristic of the present invention. Decreases curing properties. Therefore, in the present invention, Al is 0.02%
Limited to the following. In order to stably obtain high strain age hardening characteristics, the content is 0.015% or less.

【００２３】Ｎ：0.0050〜0.0250％ Ｎは、本発明において最も重要な元素である。本発明で
は、適量のＮを含有して、製造条件を制御することによ
り、冷延製品で必要かつ十分な量の固溶状態のＮを確保
し、それによって固溶強化と歪時効硬化での強度（Ｙ
Ｓ、ＴＳ）上昇効果が十分に発揮され、ＴＳ：440MPa以
上で、塗装焼付硬化量（ＢＨ量）40MPa 以上、歪時効処
理前後での引張強さの増加量ΔＴＳ50MPa 以上という本
発明鋼板の機械的性質要件を安定して満足することがで
きる。これにより、完成品（部品）の耐衝撃特性、耐疲
労特性も向上する。また、固溶Ｎによる強化を活用する
ことにより、Ｃ、Si、Mn等の添加量を低減でき、溶接
性、塗装性の低下を防止できる。N: 0.0050-0.0250% N is the most important element in the present invention. In the present invention, by containing an appropriate amount of N and controlling the manufacturing conditions, a necessary and sufficient amount of N in the solid solution state in the cold-rolled product is ensured, whereby the solid solution strengthening and strain aging hardening are achieved. Strength (Y
S, TS) The mechanical effect of the steel sheet of the present invention is sufficiently exhibited, with TS: 440 MPa or more, paint bake hardening amount (BH amount) 40 MPa or more, and increase in tensile strength before and after strain aging treatment ΔTS50 MPa or more. Property requirements can be stably satisfied. Thereby, impact resistance and fatigue resistance of the finished product (part) are also improved. Further, by utilizing the strengthening by solid solution N, the amount of C, Si, Mn, etc. added can be reduced, and a decrease in weldability and paintability can be prevented.

【００２４】Ｎが0.0050％未満では、上記の強度上昇効
果が安定して現れにくい。一方、Ｎが0.0250％を超える
と、鋼板の内部欠陥発生率が高くなるとともに、連続鋳
造時のスラブ割れなどが多発するようになる。このた
め、Ｎは0.0050〜0.0250％の範囲とした。なお、製造工
程全体を考慮した材質の安定性・歩留り向上の観点から
は、Ｎは0.0070〜0.0170％の範囲とするのがより好まし
い。なお、本発明範囲内のＮ量であれば、スポット溶
接、アーク溶接等の溶接性への悪影響は全くない。If N is less than 0.0050%, the above-mentioned effect of increasing the strength is unlikely to appear stably. On the other hand, when N exceeds 0.0250%, the internal defect generation rate of the steel sheet increases, and slab cracks and the like during continuous casting occur frequently. Therefore, N is set in the range of 0.0050 to 0.0250%. Note that N is more preferably in the range of 0.0070 to 0.0170% from the viewpoint of improving the stability and yield of the material in consideration of the entire manufacturing process. If the N content is within the range of the present invention, there is no adverse effect on weldability such as spot welding and arc welding.

【００２５】固溶状態のＮ：0.0010％以上 冷延製品で固溶強化により十分な強度が確保され、さら
にＮによる歪時効硬化現象が十分に発揮されるには、鋼
中に固溶状態のＮ（固溶Ｎともいう）が0.0010％以上の
量（濃度）で存在する必要がある。ここで、固溶Ｎ量
は、鋼中の全Ｎ量から析出Ｎ量を差し引いて求めるもの
とする。なお、析出Ｎ量の分析法としては、本発明者ら
が種々の分析法を比較検討した結果によれば、定電位電
解法を用いた電解抽出分析法により求めるのが有効であ
る。なお抽出分析に用いる地鉄を溶解する方法として、
酸分解法、ハロゲン法および電解法がある。この中で、
電解法は炭化物、窒化物などの極めて不安定な析出物を
分解させることなく、安定して地鉄のみを溶解できる。
電解液としてはアセチル・アセトン系を用いて、定電位
にて電解する。本発明では定電位電解法を用いて析出Ｎ
量を測定した結果が、実際の部品強度ともっともよい対
応を示した。N in the solid solution state: 0.0010% or more In order to secure sufficient strength by solid solution strengthening in a cold-rolled product and to sufficiently exhibit the strain aging hardening phenomenon due to N, the solid solution state in the steel is required. N (also referred to as solid solution N) must be present in an amount (concentration) of 0.0010% or more. Here, the amount of solute N is determined by subtracting the amount of precipitated N from the total amount of N in steel. As a method of analyzing the amount of deposited N, according to the results of comparative studies of various analysis methods by the present inventors, it is effective to obtain the amount by the electrolytic extraction analysis method using the potentiostatic electrolysis method. In addition, as a method of dissolving ground iron used for extraction analysis,
There are an acid decomposition method, a halogen method and an electrolytic method. In this,
The electrolysis method can stably dissolve only ground iron without decomposing extremely unstable precipitates such as carbides and nitrides.
Electrolysis is performed at a constant potential using an acetyl-acetone system as the electrolytic solution. In the present invention, the deposition N
The measured results showed the best correspondence with the actual part strength.

【００２６】このようなことから、本発明では、定電位
電解法により抽出した残渣を化学分解して残渣中のＮ量
を求め、これを析出Ｎ量とする。なお、より高いＢＨ
量、ΔＴＳを得るためには、固溶Ｎ量は0.0020％以上、
さらに高い値を得るためには、0.0030％以上とするのが
好ましい。 Ｎ／Al（Ｎ含有量とAl含有量の比）：0.3 以上 製品状態で、固溶Ｎを0.0010％以上安定させて残留させ
るためには、Ｎを強力に固定する元素であるAlの量を制
限する必要がある。本発明の組成範囲内のＮ含有量とAl
含有量の組合せを広範囲に変えた鋼板について検討した
結果、冷延製品での固溶Ｎを0.0010％以上とし、安定し
て高い歪時効硬化特性を得るには、Al量を0.02％以下と
低く限定した場合、Ｎ／Alを0.3 以上とすることが必要
であることがわかった。すなわち、Al含有量は（Ｎ含有
量）／0.3 以下に制限される。In view of the above, in the present invention, the residue extracted by the potentiostatic electrolysis method is chemically decomposed to determine the amount of N in the residue, which is defined as the amount of deposited N. In addition, higher BH
In order to obtain the amount, ΔTS, the amount of solute N should be 0.0020% or more,
In order to obtain an even higher value, the content is preferably set to 0.0030% or more. N / Al (ratio between N content and Al content): 0.3 or more In order to stably maintain solid solution N at 0.0010% or more in the product state, the amount of Al, an element that strongly fixes N, must be adjusted. It needs to be restricted. N content and Al within the composition range of the present invention
As a result of examining steel sheets with various combinations of content, it was found that in order to obtain a solid solution N of 0.0010% or more in cold-rolled products and obtain stable and high strain age hardening characteristics, the Al content should be as low as 0.02% or less. In the case of limitation, it was found that it was necessary to make N / Al 0.3 or more. That is, the Al content is limited to (N content) /0.3 or less.

【００２７】本発明では、上記した組成に加えてさら
に、次ａ群〜ｄ群 ａ群：Ｂ：0.0003〜0.01％、Cu：0.005 〜1.5 ％、Ni：
0.005 〜1.5 ％、Cr：0.05〜1.0 ％のうちの１種または
２種以上 ｂ群：Ti、Nb、Ｖ、Zrのうちの１種または２種以上を合
計で0.002 〜0.03％ ｃ群：Ca、REM の１種または２種を合計で0.0010〜0.01
0 ％のうちから１群または２群以上を必要に応じ含有す
るのが好ましい。In the present invention, in addition to the above composition, the following groups a to d: a group: B: 0.0003 to 0.01%, Cu: 0.005 to 1.5%, Ni:
0.005 to 1.5%, Cr: one or more of 0.05 to 1.0% b group: one or more of Ti, Nb, V, and Zr 0.002 to 0.03% in total C group: Ca , REM 1 or 2 in total 0.0010-0.01
It is preferable to contain one or more groups out of 0% as required.

【００２８】ａ群：Ｂ：0.0003〜0.01％、Cu：0.005 〜
1.5 ％、Ni：0.005 〜1.5 ％、Cr：0.05〜1.0 ％のうち
の１種または２種以上 ａ群の元素：Ｂ、Cu、Ni、Crは、いずれもMnと同様に、
焼入れ性を向上させる元素であり、必要に応じ、１種ま
たは２種以上を選択して含有できる。Ｂは、焼入れ性を
向上させ、さらに延性の向上に有効な元素であり、この
ような効果は、0.0003％以上の含有で認められる。一
方、0.01％を超える含有は、Ｂが析出物となり、加工性
が低下する。このため、Ｂは0.0003〜0.01％に限定する
のが好ましい。Group a: B: 0.0003 to 0.01%, Cu: 0.005 to
One or more of 1.5%, Ni: 0.005 to 1.5%, Cr: 0.05 to 1.0% Elements of group a: B, Cu, Ni, Cr are the same as Mn,
It is an element that improves quenching properties, and one or more kinds can be selected and contained as necessary. B is an element effective for improving hardenability and further improving ductility, and such an effect is recognized when the content is 0.0003% or more. On the other hand, when the content exceeds 0.01%, B becomes a precipitate and the workability is reduced. Therefore, B is preferably limited to 0.0003 to 0.01%.

【００２９】Cuは、焼入れ性を向上させ、鋼板の強度を
増加させる元素であり、このような効果は0.05％以上の
含有で認められるが、1.5 ％を超えると、熱間圧延での
スケール疵が多発する。このため、Cuは0.05〜1.5 ％と
するのが好ましい。Niは、焼入れ性を向上させ、鋼板の
強度を増加させる元素であり、また含有しても鋼板のめ
っき性への影響が少ない元素であり、必要に応じ含有で
きる。上記した効果は、0.005 ％以上の含有で認められ
るが、1.5 ％を超える含有は、強度が増加しすぎて、延
性を低下させ、プレス成形を加工性を低下させる。この
ため、Niは0.005 〜1.5 ％とするのが好ましい。Cu is an element that improves the hardenability and increases the strength of the steel sheet. Such an effect is recognized at a content of 0.05% or more, but when it exceeds 1.5%, scale flaws in hot rolling occur. Frequently occur. For this reason, Cu is preferably set to 0.05 to 1.5%. Ni is an element that improves the hardenability and increases the strength of the steel sheet, and even if contained, has little effect on the plating property of the steel sheet, and can be contained as necessary. The above-mentioned effects are recognized at a content of 0.005% or more, but a content of more than 1.5% excessively increases the strength, lowers the ductility, and lowers the workability of press molding. For this reason, Ni is preferably set to 0.005 to 1.5%.

【００３０】Crは、焼入れ性を向上させ、鋼板の強度を
増加させるとともに、残留γの分布状態を微細分散とす
る作用を有し、延性を向上させる効果を有する元素であ
る。このような効果は、0.05％以上の含有で認められ
る。一方、1.0 ％を超える含有は、めっき濡れ性を阻害
する。このため、Crは0.05〜1.0 ％とするのが好まし
い。Cr is an element having the effect of improving the hardenability, increasing the strength of the steel sheet, finely dispersing the distribution of the residual γ, and improving the ductility. Such an effect is recognized at a content of 0.05% or more. On the other hand, when the content exceeds 1.0%, plating wettability is impaired. For this reason, Cr is preferably set to 0.05 to 1.0%.

【００３１】ｂ群：Ti、Nb、Ｖ、Zrのうちの１種または
２種以上を合計で0.002 〜0.03％ ｂ群の元素：Ti、Nb、Ｖ、Zrは、いずれも、結晶粒を微
細化し、延性を改善する効果を有する元素であり、必要
に応じ選択して含有できる。しかし、過剰な含有は固溶
状態のＮを減少させる。このようなことから、Ti、Nb、
Ｖ、Zrのうちの１種または２種以上を合計で0.002 〜0.
03％の範囲に限定するのが好ましい。Group b: one or more of Ti, Nb, V, and Zr in total 0.002 to 0.03% Elements of Group b: Ti, Nb, V, and Zr are all fine crystal grains. It is an element that has the effect of turning into a ductile material and improving ductility, and can be selectively contained as necessary. However, an excessive content reduces N in the solid solution state. For these reasons, Ti, Nb,
One or two or more of V and Zr are added in a total amount of 0.002 to 0.
Preferably, it is limited to the range of 03%.

【００３２】ｃ群：Ca、REM の１種または２種を合計で
0.0010〜0.010 ％ ｃ群の元素：Ca、REM は、いずれも介在物の形態制御に
役立つ元素であり、特に伸びフランジ成形性の要求があ
る場合には、単独または複合して含有するのが好まし
い。その場合、ｃ群の元素の合計で、0.0010％未満では
介在物の形態制御効果が不足し、一方、0.010 ％を超え
ると表面欠陥の発生が目立つようになる。このため、ｃ
群の元素は合計で0.0010〜0.010 ％の範囲に限定するの
が好ましい。Group c: one or two of Ca and REM in total
0.0010-0.010% Elements of group c: Ca and REM are both elements that are useful for controlling the morphology of inclusions. Particularly when stretch flangeability is required, it is preferable to include them alone or in combination. . In this case, if the total of the elements of group c is less than 0.0010%, the effect of controlling the morphology of inclusions is insufficient, while if it exceeds 0.010%, the occurrence of surface defects becomes conspicuous. Therefore, c
Preferably, the elements of the group are limited to a total range of 0.0010-0.010%.

【００３３】上記した成分以外の残部は、Feおよび不可
避的不純物からなる。不可避的不純物としては、Ｓ：0.
02％以下が許容できる。Ｓは、鋼板中では介在物として
存在し、鋼板の延性、さらには耐食性の劣化をもたらす
元素であり、できるだけ低減するのが望ましい。なお、
特に良好な加工性が要求される用途においては、0.015
％以下、さらに伸びフランジ性の要求レベルが高い場合
は、Ｓは0.008 ％以下に低減するのが好ましい。また、
歪時効硬化特性を安定して高レベルに維持するために
は、詳細な機構は不明であるが、Ｓを0.008 ％以下まで
低減するのが好ましい。The balance other than the above components consists of Fe and unavoidable impurities. As inevitable impurities, S: 0.
02% or less is acceptable. S is an element that exists as an inclusion in the steel sheet and causes the deterioration of the ductility and the corrosion resistance of the steel sheet, and is desirably reduced as much as possible. In addition,
For applications requiring particularly good workability, 0.015
%, The S is preferably reduced to 0.008% or less when the required level of stretch flangeability is high. Also,
In order to stably maintain the strain age hardening characteristics at a high level, the detailed mechanism is unknown, but it is preferable to reduce S to 0.008% or less.

【００３４】次に、本発明鋼板の組織について説明す
る。 フェライト相の体積率：20〜80％ 本発明の冷延鋼板は、高度な加工性が要求される自動車
用鋼板等の使途を目的としており、延性を確保するため
に、フェライト相を体積率で20〜80％含む組織とする。
フェライト相の体積率が20％未満では、高度な加工性が
要求される自動車用鋼板として必要な延性を確保するこ
とが困難となる。なお、さらに良好な延性が要求される
場合は、フェライト相の体積率は30％以上とするのが好
ましい。フェライト相の体積率が80％を超えると、複合
組織の利点が少なくなる。このため、フェライト相は20
〜80％とした。Next, the structure of the steel sheet of the present invention will be described. The volume fraction of the ferrite phase: 20 to 80% The cold-rolled steel sheet of the present invention is intended for use in steel sheets for automobiles and the like, which require high workability. Organization that contains 20-80%.
If the volume fraction of the ferrite phase is less than 20%, it becomes difficult to secure the required ductility as a steel sheet for automobiles requiring high workability. In the case where better ductility is required, the volume ratio of the ferrite phase is preferably 30% or more. When the volume fraction of the ferrite phase exceeds 80%, the advantage of the composite structure is reduced. For this reason, the ferrite phase
8080%.

【００３５】ベイナイト相の体積率：10〜60％ 本発明の冷延鋼板は、高度な加工性が要求される自動車
用高張力鋼板等の使途を目的としており、延性と強度の
優れたバランスを確保するために、フェライト相に加え
てさらに、10〜60％のベイナイト相を含有する。ベイナ
イト相の体積率が10％未満では、必要な延性、強度を確
保することが困難となる。なお、さらに良好な延性が要
求される場合は、ベイナイト相の体積率は15％以上とす
るのが好ましい。ベイナイト相の体積率が60％を超える
と、延性の低下が著しくなる。このため、ベイナイト相
は10〜60％とした。The volume fraction of bainite phase: 10 to 60% The cold-rolled steel sheet of the present invention is intended for use in high-strength steel sheets for automobiles and the like, which require high workability, and has an excellent balance between ductility and strength. To ensure, in addition to the ferrite phase, it also contains a 10-60% bainite phase. When the volume fraction of the bainite phase is less than 10%, it becomes difficult to secure necessary ductility and strength. In the case where better ductility is required, the volume fraction of the bainite phase is preferably set to 15% or more. When the volume fraction of the bainite phase exceeds 60%, the ductility is significantly reduced. For this reason, the bainite phase is set to 10 to 60%.

【００３６】残留オーステナイト相の体積率：3.0 ％以
上 本発明の冷延鋼板では、高延性を確保するために、体積
率で、3.0 ％以上の残留オーステナイト（γ）相を含有
する。これにより、引張強さ：590MPa級鋼板では35％以
上、780MPa級鋼板では30％以上の伸びを確保できる。残
留γ相量の上限については特に限定しないが、実質的に
は15％程度が上限と考えられる。本発明においては、多
量のＮを含有し、しかも固溶状態で残存させることによ
り、極めて安定して残留γ量を確保できる。Volume fraction of retained austenite phase: 3.0% or more The cold-rolled steel sheet of the present invention contains a retained austenite (γ) phase at a volume fraction of 3.0% or more to ensure high ductility. As a result, tensile strength: elongation of at least 35% for a 590 MPa class steel sheet and at least 30% for a 780 MPa steel sheet can be secured. Although the upper limit of the amount of the residual γ phase is not particularly limited, it is considered that the upper limit is substantially about 15%. In the present invention, a large amount of N is contained and is left in a solid solution state, so that the amount of residual γ can be secured extremely stably.

【００３７】なお、上記した相以外の相としては、若干
量（10％以下）のマルテンサイト相が許容できる。上記
した組成と組織を有する本発明の冷延鋼板は、引張強さ
ＴＳが440MPa以上で、延性、歪時効硬化特性に優れた冷
延鋼板であり、プレス成形−塗装焼付処理後に降伏応力
および引張強さとも増加し、耐衝撃特性に優れた完成部
品となる。As a phase other than the above-mentioned phases, a slight amount (10% or less) of a martensite phase is acceptable. The cold-rolled steel sheet of the present invention having the above-described composition and structure has a tensile strength TS of 440 MPa or more, is a cold-rolled steel sheet having excellent ductility and strain age hardening properties, and has a yield stress and a tensile strength after press forming-paint baking treatment. The strength also increases, resulting in a finished part with excellent impact resistance.

【００３８】本発明において、「歪時効硬化特性に優れ
た」とは、上記したように、引張歪５％の予変形後、17
0 ℃の温度に20min 保持する条件で時効処理したとき、
この時効処理前後の変形応力増加量（ＢＨ量と記す；Ｂ
Ｈ量＝時効処理後の降伏応力−時効処理前の予変形応
力）が40MPa 以上であり、かつ歪時効処理（前記予変形
＋前記時効処理）前後の引張強さ増加量（ΔＴＳと記
す；ΔＴＳ＝時効処理後の引張強さ−予変形前の引張強
さ）が50MPa 以上であることを意味する。In the present invention, "excellent in strain age hardening characteristics" means that after pre-deformation of 5% tensile strain, 17
When subjected to aging treatment at a temperature of 0 ° C for 20 minutes,
The amount of increase in deformation stress before and after this aging treatment (referred to as BH amount; B
H content = yield stress after aging treatment-pre-deformation stress before aging treatment) is 40 MPa or more, and the amount of increase in tensile strength before and after strain aging treatment (pre-deformation + aging treatment) (denoted as ΔTS; ΔTS = Tensile strength after aging treatment-tensile strength before pre-deformation) is 50 MPa or more.

【００３９】歪時効硬化特性を規定する場合、予歪（予
変形）量が重要な因子となる。本発明者らは、自動車用
鋼板に適用される変形様式を想定して、歪時効硬化特性
に及ぼす予歪量の影響について調査し、その結果、前
記変形様式における変形応力は、極めて深い絞り加工の
場合を除き、概ね１軸相当歪（引張歪）量で整理できる
こと、実部品ではこの１軸相当歪量が概ね５％を上回
っていること、部品強度が、予歪５％の歪時効処理後
に得られる強度（ＹＳおよびＴＳ）と良く対応すること
を突き止めた。この知見をもとに、本発明では、歪時効
処理の予変形を引張歪５％に定めた。When defining the strain age hardening characteristics, the amount of pre-strain (pre-deformation) is an important factor. The present inventors have investigated the effect of the amount of pre-strain on the strain age hardening characteristics, assuming a deformation mode applied to a steel sheet for automobiles. As a result, the deformation stress in the deformation mode is extremely deep drawing. Except in the case of (1), it is possible to arrange by the amount of strain (tensile strain) equivalent to one axis. In actual parts, the amount of strain equivalent to one axis is more than 5%. It has been found that they correspond well to the strengths (YS and TS) obtained later. Based on this finding, in the present invention, the pre-deformation of the strain aging treatment was set to 5% tensile strain.

【００４０】従来の塗装焼付け処理条件は、170 ℃×20
min が標準として採用されている。なお、多量の固溶Ｎ
を含む本発明鋼板に５％以上の歪が加わる場合は、より
緩やかな（低温側の）処理でも硬化が達成され、言い換
えれば時効条件をより幅広くとることが可能である。ま
た、一般に、硬化量を稼ぐには、過度の時効で軟化させ
ない限りにおいて、より高温で、より長時間保持するこ
とが有利である。Conventional paint baking conditions are 170 ° C. × 20
min is adopted as a standard. A large amount of solid solution N
When a strain of 5% or more is applied to the steel sheet of the present invention, the hardening is achieved even with a milder (lower temperature) treatment, in other words, the aging condition can be broadened. In general, in order to increase the amount of curing, it is advantageous to hold at a higher temperature and for a longer time as long as the material is not softened by excessive aging.

【００４１】具体的に述べると、本発明鋼板では、予変
形後に硬化が顕著となる加熱温度の下限は概ね100 ℃で
ある。一方、加熱温度が300 ℃を超えると硬化が頭打ち
となり、逆にやや軟化する傾向が現れるほか、熱歪やテ
ンパーカラーの発生が目立つようになる。また、保持時
間については、加熱温度200 ℃程度のとき概ね30ｓ程度
以上とすれば略十分な硬化が達成される。さらに大きな
安定した硬化を得るには保持時間60ｓ以上とするのが好
ましい。しかし、20min を超える保持では、さらなる硬
化を望みえないばかりか、生産効率も著しく低下して実
用面では不利である。Specifically, in the steel sheet of the present invention, the lower limit of the heating temperature at which the hardening becomes remarkable after pre-deformation is about 100 ° C. On the other hand, if the heating temperature exceeds 300 ° C., the curing hardens, and on the contrary, it tends to soften slightly, and the occurrence of heat distortion and temper color becomes conspicuous. If the holding time is about 30 seconds or more when the heating temperature is about 200 ° C., almost sufficient curing can be achieved. In order to obtain even larger stable curing, the holding time is preferably 60 seconds or more. However, if the holding time exceeds 20 minutes, not only no further curing can be expected, but also the production efficiency is significantly reduced, which is disadvantageous in practical use.

【００４２】以上のことから、本発明では、時効処理条
件として従来の塗装焼付処理条件の加熱温度である170
℃、保持時間を20min で評価すると定めた。従来の塗装
焼付け型鋼板では十分な硬化が達成されない低温加熱・
短時間保持の時効処理条件下でも、本発明鋼板では大き
な硬化が安定的に達成される。なお、加熱の仕方はとく
に制限されず、通常の塗装焼付けに採用されている炉に
よる雰囲気加熱のほか、たとえば誘導加熱や、無酸化
炎、レーザ、プラズマなどによる加熱などのいずれも好
ましく用いうる。From the above, according to the present invention, the aging treatment condition is the heating temperature of the conventional paint baking treatment condition of 170 ° C.
It was determined that the evaluation was performed at 20 ° C. and a holding time of 20 min. Low-temperature heating and
Even under the condition of aging treatment for a short time, large hardening is stably achieved in the steel sheet of the present invention. The method of heating is not particularly limited, and in addition to atmospheric heating using a furnace employed for normal coating baking, any of induction heating, heating using a non-oxidizing flame, laser, plasma, or the like can be preferably used.

【００４３】自動車用の部品強度は外部からの複雑な応
力負荷に抗しうる必要があり、それゆえ素材鋼板では小
さな歪域での強度特性だけでなく大きな歪域での強度特
性も重要となる。本発明者らはこの点に鑑み、自動車部
品の素材となすべき本発明鋼板のＢＨ量を40MPa 以上と
するとともに、ΔＴＳ量を50MPa 以上とする。なお、よ
り好ましくは、ＢＨ量60 MPa以上、ΔＴＳ50MPa 以上と
する。ＢＨ量とΔＴＳ量をより大きくするには、時効処
理の際の加熱温度をより高温側に、および／または、保
持時間をより長時間側に、設定すればよい。It is necessary that the strength of automobile parts be able to withstand complicated external stress loads. Therefore, not only the strength characteristics in a small strain range but also the strength characteristics in a large strain range are important for a material steel plate. . In view of this point, the present inventors set the BH amount of the steel sheet of the present invention, which is to be used as a material for automobile parts, at 40 MPa or more and the ΔTS amount at 50 MPa or more. More preferably, the BH amount is 60 MPa or more and ΔTS50 MPa or more. To increase the BH amount and the ΔTS amount, the heating temperature during the aging treatment may be set to a higher temperature and / or the holding time may be set to a longer time.

【００４４】また、本発明鋼板は、成形加工されない状
態では、室温で１年程度の長時間放置されても時効劣化
（ＹＳが増加しかつＥｌ（伸び）が減少する現象）は起
こらないという、従来にない利点が備わっている。とこ
ろで、本発明の効果は製品板厚が比較的厚い場合でも発
揮されうるが、製品板厚が3.2mm を超える場合には、冷
延板焼鈍工程で必要十分な冷却速度を確保することがで
きず、連続焼鈍時に歪時効が生じ、製品として目標とす
る歪時効硬化特性が得にくくなる。したがって、本発明
鋼板の板厚は3.2 mm以下とするのが好ましい。In addition, the steel sheet of the present invention does not undergo aging deterioration (phenomenon in which YS increases and El (elongation) decreases) even when left for a long time of about one year at room temperature without being formed. It has unprecedented advantages. By the way, the effect of the present invention can be exerted even when the product sheet thickness is relatively thick, but when the product sheet thickness exceeds 3.2 mm, it is possible to secure a necessary and sufficient cooling rate in the cold rolled sheet annealing step. However, strain aging occurs during continuous annealing, making it difficult to obtain the desired strain aging hardening characteristics as a product. Therefore, the steel sheet of the present invention preferably has a thickness of 3.2 mm or less.

【００４５】また、本発明では、上記した本発明冷延鋼
板の表面に電気めっきまたは溶融めっきを施しても何ら
問題はない。これらめっき鋼板も、めっき前と同程度の
ＴＳ、ＢＨ量、ΔＴＳ量を示す。めっきの種類として
は、電気亜鉛めっき、溶融亜鉛めっき、合金化溶融亜鉛
めっき、電気錫めっき、電気クロムめっき、電気ニッケ
ルめっき等、いずれも好ましく適用しうる。In the present invention, there is no problem even if the surface of the cold-rolled steel sheet of the present invention is electroplated or hot-dipped. These plated steel sheets also exhibit the same amount of TS, BH and ΔTS as before plating. As the type of plating, any of electrogalvanizing, hot-dip galvanizing, alloyed hot-dip galvanizing, electrotin plating, electrochromic plating, and electronickel plating can be preferably applied.

【００４６】次に、本発明鋼板の製造方法について説明
する。本発明で使用する薄鋼板は、上記した組成を有す
るスラブを、加熱し熱間圧延により熱延板とし、ついで
該熱延板に冷間圧延を施して、所望の板厚に調整した冷
延板を用いる。スラブ加熱温度や、熱間圧延、冷間圧延
の圧延条件はとくに限定する必要はなく、所望の板厚の
冷延鋼板が得られればよい。Next, a method for producing the steel sheet of the present invention will be described. The thin steel sheet used in the present invention is obtained by heating a slab having the above composition to a hot-rolled sheet by hot rolling, and then subjecting the hot-rolled sheet to cold rolling to adjust the thickness to a desired value. Use a plate. The slab heating temperature and the rolling conditions of hot rolling and cold rolling are not particularly limited, as long as a cold-rolled steel sheet having a desired thickness is obtained.

【００４７】本発明では、質量％で、Ｃ：0.05〜0.30
％、Si：0.4 〜2.0 ％、Mn：0.7 〜3.0 ％、Ｐ：0.08％
以下、Al：0.02％以下、Ｎ：0.0050〜0.0250％を含み、
かつＮ／Alが0.3 以上を含有するこれら薄鋼板に、連続
焼鈍ラインを用いて、焼鈍処理を施す。焼鈍処理の加熱
温度は、（Ａc1変態点）〜（Ａc3変態点＋50℃）の間の
温度とする。本発明では、製品板で所定量の残留γを確
保するために、焼鈍処理の加熱温度をＡc1変態点以上と
するのが好ましい。Ａc1変態点以上に加熱することによ
り、フェライトとオーステナイト（γ）との２相に相分
離が生じ、冷却後に残留γを生成させる。一方、加熱温
度がＡc3変態点を超えても、冷却中にフェライトとオー
ステナイトへの２相分離が起こり、冷却後に残留γが生
成する。しかし、加熱温度が（Ａc3変態点＋50℃）を超
えると、焼鈍処理中に結晶粒の成長が起こり、延性が低
下する。このようなことから、焼鈍処理の加熱温度は
（Ａc1変態点）〜（Ａc3変態点＋50℃）の間の温度とす
るのが好ましい。なお、加熱温度での保持時間は特に限
定しないが、20〜60ｓとするのが望ましい。In the present invention, C: 0.05 to 0.30 by mass%.
%, Si: 0.4 to 2.0%, Mn: 0.7 to 3.0%, P: 0.08%
Hereinafter, Al: 0.02% or less, N: 0.0050 to 0.0250%,
An annealing treatment is performed on these thin steel sheets having N / Al of 0.3 or more using a continuous annealing line. The heating temperature in the annealing treatment is a temperature between (Ac 1 transformation point) and (Ac 3 transformation point + 50 ° C.). In the present invention, in order to secure a predetermined amount of residual γ in the product sheet, it is preferable that the heating temperature of the annealing treatment is set to the Ac 1 transformation point or higher. By heating above the Ac 1 transformation point, phase separation occurs between the two phases of ferrite and austenite (γ), and residual γ is formed after cooling. On the other hand, even if the heating temperature exceeds the Ac 3 transformation point, two-phase separation into ferrite and austenite occurs during cooling, and residual γ is generated after cooling. However, when the heating temperature exceeds (Ac 3 transformation point + 50 ° C.), crystal grains grow during the annealing treatment, and ductility decreases. For this reason, the heating temperature of the annealing treatment is preferably set to a temperature between (Ac 1 transformation point) to (Ac 3 transformation point + 50 ° C). The holding time at the heating temperature is not particularly limited, but is preferably 20 to 60 s.

【００４８】ついで、鋼板は加熱温度から、少なくとも
600 ℃から500 ℃の範囲を５〜 150℃／ｓの冷却速度
で、350 〜500 ℃の温度範囲まで急冷される冷却処理を
施される。冷却速度が５℃／ｓ未満では、パーライト変
態が起こり、残留γの形成が抑制され、結果として延性
が劣化する。一方、冷却速度が150 ℃／ｓを超えると、
フェライト相に多量の固溶状態のＣが残留し、残留γの
形成が抑制される。このようなことから、加熱温度か
ら、350 〜500 ℃の温度範囲までの冷却速度を５〜 150
℃／ｓとするのが好ましい。なお、このような急冷は、
少なくとも600 ℃から500 ℃の範囲のみでよい。これ
は、600 ℃から500 ℃の温度範囲では、パーライト変態
が顕著となるためである。本発明では、600 ℃から500
℃の温度範囲以外の領域はこのような冷却速度の限定は
必要としない。Next, the steel sheet is heated at least from the heating temperature.
A cooling process is performed in which the temperature is rapidly cooled from a range of 600 ° C to 500 ° C at a cooling rate of 5 to 150 ° C / s to a temperature range of 350 to 500 ° C. If the cooling rate is less than 5 ° C./s, pearlite transformation occurs, formation of residual γ is suppressed, and as a result, ductility is deteriorated. On the other hand, if the cooling rate exceeds 150 ° C / s,
A large amount of C in the solid solution state remains in the ferrite phase, and formation of residual γ is suppressed. For this reason, the cooling rate from the heating temperature to the temperature range of 350 to 500 ° C should be 5 to 150 ° C.
C / s is preferred. In addition, such rapid cooling
At least only in the range of 600 ° C to 500 ° C. This is because the pearlite transformation becomes remarkable in the temperature range of 600 ° C to 500 ° C. In the present invention, from 600 ° C to 500 ° C
Regions outside the temperature range of ° C. do not require such a cooling rate limitation.

【００４９】ついで、350 〜500 ℃の温度範囲で、30ｓ
以上の保持を行う保持処理を施される。350 〜500 ℃の
温度範囲で保持処理を行うことにより、γの一部がベイ
ナイトに変態し、その際にＣが未変態γに濃化し、γを
安定化する。これにより、室温まで冷却した後もオース
テナイト状態を保ち、残留γになる。このような反応は
350 ℃から500 ℃の範囲で顕著に起こるため、保持処理
の温度が500 ℃超えでは、炭化物が形成されやすくな
り、オーステナイトへのＣの濃縮が促進されず残留γの
形成が阻害される。また、保持処理の温度が350 ℃未満
では、上記した反応に長時間を要するため、所定量の残
留γが形成されない。なお、十分な残留γ量を得るため
には、保持処理の時間は30ｓ以上とするのが好ましい。
なお、残留γを安定して確保するためには60ｓ以上とす
るのがより好ましい。また、保持処理の時間は600 ｓ以
下とするのが生産性の観点から好ましい。なお、本発明
でいう保持は、350 ℃から500 ℃の温度範囲における徐
加熱や緩冷却としてもよい。Then, in a temperature range of 350 to 500 ° C., for 30 seconds
A holding process for holding the above is performed. By performing the holding treatment in the temperature range of 350 to 500 ° C., part of γ is transformed into bainite, and at that time, C is concentrated to untransformed γ, and γ is stabilized. As a result, the austenite state is maintained even after cooling to room temperature, resulting in residual γ. Such a reaction
Since the temperature significantly increases in the range of 350 ° C. to 500 ° C., if the temperature of the holding treatment exceeds 500 ° C., carbides are easily formed, and the concentration of C in austenite is not promoted and the formation of residual γ is inhibited. On the other hand, when the temperature of the holding treatment is lower than 350 ° C., the above-mentioned reaction takes a long time, so that a predetermined amount of residual γ is not formed. In order to obtain a sufficient amount of residual γ, it is preferable that the time of the holding process is 30 s or more.
In order to stably maintain the residual γ, it is more preferable to set it to 60 s or more. Further, it is preferable from the viewpoint of productivity that the holding processing time is set to 600 s or less. The holding in the present invention may be gradual heating or slow cooling in a temperature range of 350 ° C. to 500 ° C.

【００５０】[0050]

【実施例】表１に示す組成の溶鋼を転炉で溶製し、連続
鋳造法でスラブとした。これらスラブを1150℃に加熱し
たのち、熱間圧延を行い、熱延板とした。なお、熱間圧
延の仕上圧延終了温度を850 ℃から900 ℃の範囲とし
た。これら熱延板を、酸洗した後、冷間圧延を施し冷延
板とした。ついで、これら冷延板に、連続焼鈍ライン
（CAL ）にて、表２に示す条件の焼鈍処理、冷却・保持
処理を施した。なお、焼鈍の加熱温度から680 ℃までは
徐冷（冷却速度：1.5 ℃／ｓ）とし、680 ℃から急冷し
た。EXAMPLE Molten steel having the composition shown in Table 1 was melted in a converter and made into a slab by a continuous casting method. After heating these slabs to 1150 ° C., hot rolling was performed to obtain hot rolled sheets. The finish rolling end temperature of the hot rolling was in the range of 850 ° C to 900 ° C. These hot-rolled sheets were pickled and then cold-rolled to obtain cold-rolled sheets. Next, these cold rolled sheets were subjected to an annealing treatment, a cooling and holding treatment under the conditions shown in Table 2 in a continuous annealing line (CAL). The temperature was gradually cooled from the annealing heating temperature to 680 ° C. (cooling rate: 1.5 ° C./s) and rapidly cooled from 680 ° C.

【００５１】得られた鋼板について、固溶Ｎ量、微視組
織、引張特性、歪時効硬化特性を調査した。 （１）固溶Ｎ量の調査 固溶Ｎ量は、化学分析により求めた鋼中の全Ｎ量から析
出Ｎ量を差し引いて求めた。析出Ｎ量は、上記した定電
位電解法を用いた分析法により求めた。 （２）微視組織 各冷延焼鈍板から試験片を採取し、圧延方向に直交する
断面（Ｃ断面）について、光学顕微鏡あるいは走査型電
子顕微鏡を用いて微視組織を撮像し、画像解析装置を用
いて、フェライトの組織分率、ベイナイトの組織分率を
求めた。また、残留γ量は、鋼板の板厚1/4tの面でＸ線
回折法により測定した。γの（211 ）および（220 ）面
とαの（200 ）、（220 ）の強度比から残留γの体積率
を算出した。 （３）引張特性 各冷延焼鈍板からJIS ５号試験片を圧延方向に採取し、
JIS Z 2241の規定に準拠して歪速度：３×10-3／ｓで引
張試験を実施し、降伏強さＹＳ、引張強さＴＳ、伸びＥ
ｌを求めた。 （４）歪時効硬化特性 各冷延焼鈍板からJIS ５号試験片を圧延方向に採取し、
予変形としてここでは５％の引張予歪を与えて、ついで
170 ℃×20min の塗装焼付処理相当の熱処理を施したの
ち、歪速度：３×10-3／ｓで引張試験を実施し、予変形
−塗装焼付処理後の引張特性（降伏応力ＹＳBH、引張強
さＴＳ）を求め、ＢＨ量＝ＹＳBH−ＹＳ 5%、ΔＴＳ＝Ｔ
ＳBH−ＴＳを算出した。なお、ＹＳ5%は、製品板を５％
予変形したときの変形応力であり、ＹＳBH、ＴＳBHは予
変形−塗装焼付処理後の降伏応力、引張強さであり、Ｔ
Ｓは製品板の引張強さである。About the obtained steel sheet, the amount of solute N, microscopic set
Weaving, tensile properties and strain age hardening properties were investigated. (1) Investigation of the amount of solute N The amount of solute N was determined from the total amount of N in steel determined by chemical analysis.
It was determined by subtracting the amount of N coming out. The amount of precipitated N is determined by the constant
It was determined by an analytical method using a potential electrolysis method. (2) Microstructure A test specimen is sampled from each cold-rolled annealed sheet and is perpendicular to the rolling direction.
For the cross section (C cross section), use an optical microscope or scanning
Image of microscopic tissue using a microscopic microscope and use an image analyzer
And the structure fractions of ferrite and bainite
I asked. The amount of residual γ was measured by X-ray
It was measured by a diffraction method. (211) and (220) planes of γ
And the volume ratio of residual γ from the intensity ratio of (200) and (220)
Was calculated. (3) Tensile properties A JIS No. 5 test piece was sampled from each cold-rolled annealed plate in the rolling direction.
Strain rate: 3 × 10 according to JIS Z 2241-3/ S
Tensile test was performed, yield strength YS, tensile strength TS, elongation E
1 was determined. (4) Strain aging hardening characteristics A JIS No. 5 test piece was sampled from each cold-rolled annealed sheet in the rolling direction.
As a pre-deformation, a tensile pre-strain of 5% is given here.
A heat treatment equivalent to a paint baking treatment at 170 ° C for 20 minutes was performed.
C, strain rate: 3 × 10-3/ S tensile test and pre-deformation
-Tensile properties after paint baking (yield stress YSBH, Tensile strength
TS), and BH amount = YSBH-YS Five%, ΔTS = T
SBH-TS was calculated. YSFive%Means 5%
Deformation stress when pre-deformed, YSBH, TSBHIs
Deformation-yield stress and tensile strength after paint baking treatment.
S is the tensile strength of the product plate.

【００５２】これらの結果を表２に示す。Table 2 shows the results.

【００５３】[0053]

【表１】 [Table 1]

【００５４】[0054]

【表２】 [Table 2]

【００５５】本発明例では、いずれも優れた延性と、優
れた歪時効硬化特性を有し、格段に高いＢＨ量、ΔＴＳ
を呈した鋼板となっており、部品耐衝撃特性の向上が期
待できる。In the examples of the present invention, all have excellent ductility and excellent strain aging hardening characteristics, and have a remarkably high BH amount and ΔTS.
It is expected to improve the impact resistance of parts.

【００５６】[0056]

【発明の効果】本発明によれば、予変形−塗装焼付処理
によりＢＨ量：40MPa 以上およびΔＴＳ：50MPa 以上
と、ともに増加する高い歪時効硬化特性と高い成形性と
を有する高張力冷延鋼板を、安定して製造でき、産業上
格段の効果を奏する。さらに本発明の高張力冷延鋼板を
自動車部品に適用した場合、塗装焼付処理などにより降
伏応力とともに引張強さも増加して安定した高い耐衝撃
特性を有する部品を得ることができる。また、使用する
鋼板の板厚を、例えば2.0mm 厚から1.6 mm厚と、従来よ
り１グレード低減することを可能とし、自動車車体の軽
量化に充分に寄与することができるという効果もある。
また、固溶Ｎによる強化を利用することにより、Si、Mn
等の他の強化元素の含有量を低減でき、溶接性、塗装性
を改善できるという効果もある。According to the present invention, a high-tensile cold-rolled steel sheet having a high strain age hardening property and a high formability, both of which are increased by pre-deformation-paint baking treatment to a BH content of 40 MPa or more and ΔTS: 50 MPa or more. Can be manufactured stably, and an industrially remarkable effect is achieved. Further, when the high-tensile cold-rolled steel sheet of the present invention is applied to an automobile part, a part having stable and high impact resistance can be obtained by increasing tensile strength together with yield stress by paint baking treatment or the like. Further, the thickness of the steel plate to be used can be reduced by one grade, for example, from 2.0 mm thickness to 1.6 mm thickness, and there is also an effect that it is possible to sufficiently contribute to weight reduction of an automobile body.
In addition, by utilizing the strengthening by solid solution N, Si, Mn
In addition, there is also an effect that the content of other strengthening elements such as the above can be reduced, and the weldability and the paintability can be improved.

───────────────────────────────────────────────────── フロントページの続き (72)発明者 古君 修 千葉県千葉市中央区川崎町１番地 川崎製 鉄株式会社技術研究所内 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Osamu Furukun 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Pref.

Claims (4)

【特許請求の範囲】[Claims] 【請求項１】 質量％で、 Ｃ：0.05〜0.30％、 Si：0.4 〜2.0 ％、 Mn：0.7 〜3.0 ％、 Ｐ：0.08％以下、 Al：0.02％以下、 Ｎ：0.0050〜0.0250％ を含み、かつＮ／Alが0.3 以上、固溶状態のＮを0.0010
％以上含有し、残部Feおよび不可避的不純物からなる組
成と、体積率で、20〜80％のフェライト相と、10〜60％
のベイナイト相と、3.0 ％以上の残留オーステナイト相
とを含む複合組織を有することを特徴とする延性および
ΔＴＳ：50MPa 以上となる歪時効硬化特性に優れた高張
力冷延鋼板。1. Mass%: C: 0.05 to 0.30%, Si: 0.4 to 2.0%, Mn: 0.7 to 3.0%, P: 0.08% or less, Al: 0.02% or less, N: 0.0050 to 0.0250% And N / Al is 0.3 or more, and N in the solid solution state is 0.0010
%, With the balance being Fe and unavoidable impurities, a ferrite phase of 20 to 80% by volume, and a 10 to 60%
A high-tensile cold-rolled steel sheet having excellent ductility and a strain age hardening property of ΔTS: 50 MPa or more, characterized by having a composite structure containing a bainite phase and a retained austenite phase of 3.0% or more. 【請求項２】 前記組成に加えてさらに、質量％で、下
記ａ群〜ｃ群のうちの１群または２群以上を含むことを
特徴とする請求項１に記載の高張力冷延鋼板。 記 ａ群：Ｂ：0.0003〜0.01％、Cu：0.005 〜1.5 ％、Ni：
0.005 〜1.5 ％、Cr：0.05〜1.0 ％のうちの１種または
２種以上 ｂ群：Ti、Nb、Ｖ、Zrのうちの１種または２種以上を合
計で0.002 〜0.03％ ｃ群：Ca、REM の１種または２種を合計で0.0010〜0.01
0 ％2. The high-tensile cold-rolled steel sheet according to claim 1, further comprising one or more of the following groups a to c in mass% in addition to the composition. Note a group: B: 0.0003 to 0.01%, Cu: 0.005 to 1.5%, Ni:
0.005 to 1.5%, Cr: one or more of 0.05 to 1.0% b group: one or more of Ti, Nb, V, and Zr 0.002 to 0.03% in total C group: Ca , REM 1 or 2 in total 0.0010-0.01
0% 【請求項３】 前記高張力冷延鋼板の板厚が3.2 mm以下
である請求項１または２に記載の高張力冷延鋼板。3. The high-tensile cold-rolled steel sheet according to claim 1, wherein the high-tensile cold-rolled steel sheet has a thickness of 3.2 mm or less. 【請求項４】 質量％で、 Ｃ：0.05〜0.30％、 Si：0.4 〜2.0 ％、 Mn：0.7 〜3.0 ％、 Ｐ：0.08％以下、 Al：0.02％以下、 Ｎ：0.0050〜0.0250％ を含み、かつＮ／Alが0.3 以上を含有する薄冷延鋼板
に、加熱温度を（Ａc1変態点）〜（Ａc3変態点＋50℃）
の間の温度とする焼鈍処理と、ついで該加熱温度から、
少なくとも600 ℃から500 ℃の範囲を５〜 150℃／ｓの
冷却速度で冷却し、350 〜500 ℃の温度範囲で30ｓ以上
の保持を行う冷却・保持処理を施すことを特徴とする、
延性およびΔＴＳ：50MPa 以上となる歪時効硬化特性に
優れた高張力冷延鋼板の製造方法。4. Mass%: C: 0.05 to 0.30%, Si: 0.4 to 2.0%, Mn: 0.7 to 3.0%, P: 0.08% or less, Al: 0.02% or less, N: 0.0050 to 0.0250% The heating temperature is set to (Ac 1 transformation point) to (Ac 3 transformation point + 50 ° C.) for a thin cold-rolled steel sheet containing 0.3 or more N / Al.
Between the annealing temperature and the heating temperature,
Cooling at least in the range of 600 ° C. to 500 ° C. at a cooling rate of 5 to 150 ° C./s, and performing a cooling / holding process of holding at a temperature of 350 to 500 ° C. for 30 seconds or more;
A method for producing a high-tensile cold-rolled steel sheet excellent in ductility and strain aging hardening characteristics of not less than 50 MPa.
JP2000127705A 2000-04-27 2000-04-27 High-tensile cold-rolled steel sheet with excellent ductility and strain age hardening characteristics and method for producing high-tensile cold-rolled steel sheet Expired - Fee Related JP4524850B2 (en)

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1512471A2 (en) 2003-09-04 2005-03-09 Nissan Motor Company, Limited Reinforced member
KR100554754B1 (en) * 2001-12-27 2006-02-24 주식회사 포스코 Method for Manufacturing Cold-rolled Steel Sheets with Ultra High Strength
KR100732733B1 (en) * 2003-05-21 2007-06-29 신닛뽄세이테쯔 카부시키카이샤 A cold-rolled steel sheet having a tensile strength of 780 mpa or more an excellent local formability and a suppressed increase in weld hardness
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Publication number Priority date Publication date Assignee Title
US7101914B2 (en) * 1998-05-04 2006-09-05 Natural Asa Isomer enriched conjugated linoleic acid compositions
KR20020031709A (en) * 2000-10-23 2002-05-03 이계안 A composition for manufacturing steel sheets having ultra high strength by local hardening
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0564215A (en) * 1991-09-03 1993-03-12 Matsushita Electric Ind Co Ltd Clip circuit for color difference signal
JPH09263838A (en) * 1996-03-28 1997-10-07 Kobe Steel Ltd Production of high strength cold rolled steel sheet excellent in stretch-flange formability
JPH11131145A (en) * 1997-10-30 1999-05-18 Nkk Corp Production of high strength and high ductility hot-dip galvanized steel sheet
JPH11293396A (en) * 1998-04-15 1999-10-26 Nkk Corp High strength hot dip galvanized steel sheet, galvannealed steel sheet, and their production

Family Cites Families (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4854976A (en) * 1988-07-13 1989-08-08 China Steel Corporation Method of producing a multi-phase structured cold rolled high-tensile steel sheet
JP2766693B2 (en) * 1989-12-29 1998-06-18 株式会社神戸製鋼所 Manufacturing method of high ductility and high strength cold rolled steel sheet with small anisotropy
JPH0823048B2 (en) * 1990-07-18 1996-03-06 住友金属工業株式会社 Method for producing hot rolled steel sheet with excellent bake hardenability and workability
JPH04333524A (en) 1991-05-09 1992-11-20 Nippon Steel Corp Production of high strength dual-phase steel sheet having superior ductility
US5328528A (en) * 1993-03-16 1994-07-12 China Steel Corporation Process for manufacturing cold-rolled steel sheets with high-strength, and high-ductility and its named article
JP3900619B2 (en) * 1996-10-31 2007-04-04 Ｊｆｅスチール株式会社 Hot rolled steel sheet, plated steel sheet, and hot rolled steel sheet manufacturing method excellent in bake hardenability and room temperature aging resistance
EP0952235B2 (en) * 1996-11-28 2015-09-30 Nippon Steel & Sumitomo Metal Corporation Method for producing high-strength steels having high impact energy absorption properties
CA2278841C (en) * 1997-01-29 2007-05-01 Nippon Steel Corporation High strength steels having excellent formability and high impact energy absorption properties, and a method for producing the same
JP3320014B2 (en) * 1997-06-16 2002-09-03 川崎製鉄株式会社 High strength, high workability cold rolled steel sheet with excellent impact resistance
EP0922777A1 (en) 1997-11-19 1999-06-16 RECHERCHE ET DEVELOPPEMENT DU GROUPE COCKERILL SAMBRE, en abrégé: RD-CS Flat product, such as sheet, made from ductile high-yield steel and process for manufacturing the same
JPH11279693A (en) * 1998-03-27 1999-10-12 Nippon Steel Corp Good workability/high strength hot rolled steel sheet excellent in baking hardenability and its production
CA2297291C (en) * 1999-02-09 2008-08-05 Kawasaki Steel Corporation High tensile strength hot-rolled steel sheet and method of producing the same
US20090127943A1 (en) * 2005-05-31 2009-05-21 Mitsuba Corporation Electric Motor, Production Method Of Stator, And Production Method Of Electric Motor

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0564215A (en) * 1991-09-03 1993-03-12 Matsushita Electric Ind Co Ltd Clip circuit for color difference signal
JPH09263838A (en) * 1996-03-28 1997-10-07 Kobe Steel Ltd Production of high strength cold rolled steel sheet excellent in stretch-flange formability
JPH11131145A (en) * 1997-10-30 1999-05-18 Nkk Corp Production of high strength and high ductility hot-dip galvanized steel sheet
JPH11293396A (en) * 1998-04-15 1999-10-26 Nkk Corp High strength hot dip galvanized steel sheet, galvannealed steel sheet, and their production

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100554754B1 (en) * 2001-12-27 2006-02-24 주식회사 포스코 Method for Manufacturing Cold-rolled Steel Sheets with Ultra High Strength
US9194015B2 (en) 2002-08-20 2015-11-24 Kobe Steel, Ltd. Dual phase steel sheet with good bake-hardening properties
JP2009144251A (en) * 2003-04-16 2009-07-02 Jfe Steel Corp High-tensile strength cold-rolled steel sheet
KR100732733B1 (en) * 2003-05-21 2007-06-29 신닛뽄세이테쯔 카부시키카이샤 A cold-rolled steel sheet having a tensile strength of 780 mpa or more an excellent local formability and a suppressed increase in weld hardness
EP1512471A2 (en) 2003-09-04 2005-03-09 Nissan Motor Company, Limited Reinforced member
US7695824B2 (en) 2003-09-04 2010-04-13 Nissan Motor Co., Ltd. Reinforced member
JP2009249733A (en) * 2008-04-10 2009-10-29 Nippon Steel Corp High-strength steel sheet having extremely reduced deterioration in aging property and having excellent baking hardenability, and method for producing the same
JP2009001909A (en) * 2008-07-31 2009-01-08 Jfe Steel Kk Manufacturing method of high-strength cold-rolled steel sheet
JP2012219282A (en) * 2011-04-04 2012-11-12 Kobe Steel Ltd Method for manufacturing high strength steel sheet excellent in stability of mechanical property
CN109923236A (en) * 2016-11-07 2019-06-21 Posco公司 The excellent ultrahigh-strength steel plates of yield ratio and its manufacturing method

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